Reducing the size of a flameless thermal oxidizer by oxygen enhancement

ABSTRACT

A flameless thermal oxidizer includes a container in which a ceramic matrix is contained, and a diptube having a passageway extending therethrough, the diptube positioned in and in communication with the ceramic matrix and in which a plurality of gaseous streams are present for combustion at the ceramic matrix, the plurality of gaseous streams including a vent stream and an oxygen stream. A related method is also provided.

BACKGROUND OF THE INVENTION

The present embodiments relate to a flameless thermal oxidizer (FTO) used to oxidize gaseous waste streams.

In order to reach a desired operating temperature in an FTO, the waste to be reacted in same must have a minimum calorific value. When a low energy content waste stream has to be completely combusted, but such stream includes therein a product of combustion temperature which is too low, a typical solution is to enrich the waste stream with a more valuable, higher calorific value gas as the fuel. This process requires an increase in air for combustion and as such, additional fuel is required as well as an increase in both the total combustion product volume and the size of the reaction chamber, all of which reduces cost effectiveness.

In a conventional FTO shown generally at 10 in FIG. 1, air and a waste stream (a vent stream from another process) which may include organic and other particular material is introduced via a diptube into a preheated porous matrix.

As the air and waste stream expands through a matrix it absorbs heat from the ceramic until the stream reaches its auto-ignition temperature, at which point it starts to react, liberate heat and deliver heat back to the ceramic matrix. Such delivered heat is then transferred back through the ceramic matrix, by a combination of conduction, convection and radiation, serving to preheat a fresh waste stream and air entering the matrix via the diptube. In such a process, a self-sustaining oxidation process is achieved, and high peak flame temperatures observed in conventional combustion systems are avoided by the transfer of heat rapidly to the ceramic matrix.

In particular, the FTO includes a container 12 or vessel with internal space 14 in which a hot ceramic matrix 16 is disposed. A top of the container 12 is provided with an opening 18 through which a diptube 20 or inlet diptube is inserted. A lower end 22 of the diptube 20 opens into the ceramic matrix 16. An upper end of the diptube above the opening 18 and external to the container 12 is provided with a plurality of inlets 24, 26, 28 (collectively “24-28”). The inlets 24-28 are connected to and in communication with an internal passage 30 extending through the diptube 20 to the lower end 22. The inlet 24 is the vent or waste inlet for providing a waste stream from an upstream process (not shown) into the internal passage 30 of the diptube 20. The inlet 26 is the air inlet introducing an air stream into the internal passage 30 of the diptube 20. The inlet 28 is the fuel inlet for providing a fuel stream to the internal passage 30 of the diptube 20. All of the streams provided by the inlets 24-28 are mixed in the internal passage 30 and are discharged from the lower end 22 of the diptube into the hot ceramic matrix 16 which provides an oxidation zone 32 extending from the lower end 22 outward and upward along the diptube. The oxidation zone 32 tapers to a reduced diameter and dissipates as it heats the ceramic matrix in the container, as shown by the arrows 34.

The container 12 is also provided with an outlet 36 or exhaust in which clean gas 38 is discharged from the ullage 40 in the container 12 above an upper surface 42 of the ceramic matrix 16. That is, the outlet 36 is in fluid communication with the ullage 40 above the surface 42 of the ceramic matrix 16, such that the latter will not be exhausted through the outlet with the clean gas 38. In effect, the vent or waste stream being introduced at the inlet 24 may contain organic and/or particulate matter which is combusted and/or filtered in the hot ceramic matrix 16 and thereafter exhausted from the ullage 40 above the matrix and through the outlet 36 to be discharged as the clean gas stream 38.

The gaseous waste stream-air mixture 24, 26 has to be sufficiently reactive and have sufficient energy content to create products of combustion able to effectively heat the ceramic matrix and to preheat the incoming waste-air mixture. This is often accomplished by an adiabatic combustion temperature which can be readily calculated on a thermodynamic basis knowing the composition and temperature of the waste and air streams.

If the waste stream-air mixture is not sufficiently reactive and the products of combustion cannot be raised to the required temperature using the inherent enthalpy of combustion of the waste stream, then supplemental fuel may be added. However, the added fuel increases operating costs, and also increases emissions and a requirement for a larger reaction vessel, due to the increased volume of combustion products.

SUMMARY OF THE INVENTION

There is therefore provided herein to replace at least a portion of the air used in the FTO to combust the waste stream with an oxygen rich stream, such that the combustion product temperature is increased without the need to use additional fuel. The present embodiments therefore reduce the volume of combustion products which results in either a smaller volume FTO being used or a higher throughput through the existing FTO while avoiding the need for additional fuel.

A flameless thermal oxidizer (FTO) provided herein includes a container in which a ceramic matrix is contained and a diptube having a passageway extending therethrough, the diptube inserted or positioned in the ceramic matrix and in which a plurality of gaseous streams are present for combustion at the ceramic matrix, the plurality of gaseous streams including at least a vent stream and an oxygen stream.

A method of operating an FTO includes introducing a plurality of gaseous streams into a heated ceramic matrix contained within the FTO, the plurality of gaseous streams including at least a vent stream and an oxygen stream.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present inventive embodiments reference may be had to the following description of exemplary embodiments considered in connection with the accompanying drawing Figures, of which:

FIG. 1 shows a side view in cross-section of a known flameless thermal oxidizer (FTO discussed above);

FIG. 2 shows a side view in cross-section of a first embodiment of an FTO according to the present invention;

FIG. 3 shows a side view in cross-section of another embodiment of an FTO according to the present invention;

FIG. 4 shows a side view in cross-section of still another embodiment of an FTO according to the present invention; and

FIG. 5 shows a side view in cross-section of still another embodiment of an FTO according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Before explaining the inventive embodiments in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, if any, since the invention is capable of other embodiments and being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

In the following description, terms such as a horizontal, upright, vertical, above, below, beneath and the like, are to be used solely for the purpose of clarity illustrating the invention and should not be taken as words of limitation. The drawings are for the purpose of illustrating the invention and are not intended to be to scale.

Referring to FIGS. 2-5, embodiments of an FTO are shown according to the present invention. Four exemplary embodiments of an FTO constructed in accordance with the present invention are illustrated in FIGS. 2-5, respectively. Elements illustrated in FIGS. 2-5 which correspond with the elements described above with respect to FIG. 1 have been designated by corresponding reference numerals increased by 100, 200, 300 and 400, respectively. The embodiments of FIGS. 3-5 are designed for use in the same manner as the embodiment of FIG. 2 unless otherwise stated.

The present embodiments include a system where an increased oxygen concentration (greater than that found in air) is used to provide the desired combustion temperature without using additional fuel and air and, in fact, reduces the overall volume of the products of combustion. As such, either an increase in capacity for the same volume reactor or a smaller reactor is needed for the same throughput. This will result in capital cost savings.

Referring to the embodiment shown at FIG. 2, a pure oxygen stream 11 is introduced into a separate inlet 13 which is connected to and in communication with the internal passage 130 of the diptube 120. The oxygen stream 11 mixes with the inlet streams 124-128 in the internal passage 130.

Referring to FIG. 3, in this embodiment the FTO 210 is provided with a pure oxygen stream 15 introduced through an inlet pipe 17 which is sized and shaped for extending into and through a substantial length of the internal passage 230 of the diptube 220. As shown in FIG. 3, a lower end 19 of the inlet pipe 17 opens at an outlet prior to or upstream of an opening at the lower end 222 of the diptube 220. This provides for mixing of the oxygen stream 15 with the inlet streams 224-228 prior to being exhausted into the oxidation zone 232.

In the embodiment shown in FIG. 4, a pure oxygen stream 21 and the inlet stream 326 for the air are combined in a pipe 23 which has an outlet 25 for the combined oxygen-airstream 27 to be introduced at an inlet 29 in gaseous communication with the internal passage 330 of the diptube 320. The oxygen-air stream 27 mixes with the vent stream 324 and the fuel stream 328 in the internal passage 330.

In the embodiment shown in FIG. 5, a pure oxygen stream 31 is mixed with the inlet streams 424-428 in a pipe 33 having an outlet 35 connected to and in communication with the internal passage 430 of the diptube 420. The pipe 33 is external to the diptube 420, wherein a construction of the pipe permits the pure oxygen stream 31 and the inlet streams 424-428 to be mixed together as shown generally at 37 whereupon said mixture 37 is introduced into the internal passage 430.

The oxygen concentration in the streams 11, 15, 21, 31 can be increased by using substantially pure oxygen introduced into air, using an oxygen rich stream mixed with air or, if in sufficient quantity, using only an oxygen rich stream.

The oxygen rich streams of the embodiments in FIGS. 2-5 may also be a by-product stream or vent stream from for example a nitrogen generator.

As discussed above, the oxygen enriched stream may be mixed with the air prior to the diptube, mixed with the air-waste mixture prior to the diptube, or kept separate from the other streams until the discharge opening at the lower end of the diptube.

The foregoing embodiments of FIGS. 2-5 provide for: a reduction in reactor size for given capacity/throughput and therefore, capital cost savings occur; an increase in reactor throughput and therefore, increased productivity; a reduction in supplemental fuel and therefore, reduced operating costs; and allowance of processing of low CV/low BTU wastes that would not normally be used in an FTO and therefore, increased flexibility.

The present embodiments may be used for example to process vent streams from processes such as for example a nitrogen generator.

It will be understood that the embodiments described herein are merely exemplary, and that a person skilled in the art may make variations and modifications without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included within the scope of the invention as provided and claimed herein. It should be understood that the embodiments described above are not only in the alternative, but can be combined. 

What is claimed is:
 1. A flameless thermal oxidizer (FTO), comprising: a container in which a ceramic matrix is contained; and a diptube having a passageway extending therethrough, the diptube positioned in the ceramic matrix and in which a plurality of gaseous streams are present for combustion at the ceramic matrix, the plurality of gaseous streams including a vent stream and an oxygen stream.
 2. The FTO of claim 1, further comprising: a first inlet connected to and in communication with the passageway for introducing the vent stream into the passageway, and a second inlet connected to and in communication with the passageway for introducing the oxygen stream into the passageway.
 3. The FTO of claim 2, wherein the first inlet is separate from the second inlet.
 4. The FTO of claim 2, wherein the second inlet comprises a pipe sized and shaped to extend into and through a length of the passageway, a distal end of the pipe having an outlet upstream of an opening at a lower end of the diptube.
 5. The FTO of claim 1, further comprising another pipe connected to and in communication with the passageway, the another pipe comprising an air stream therein for mixing with the oxygen stream in the another pipe for providing an oxygen-airstream mixture to be provided to the passageway.
 6. The FTO of claim 1, further comprising another pipe connected to and in communication with the passageway, the another pipe comprising an air stream, a fuel stream, the vent stream, and the oxygen stream for providing a mixture to be provided to the passageway.
 7. A method of operating a flameless thermal oxidizer (FTO), comprising: introducing a plurality of gaseous streams into a heated ceramic matrix contained within the FTO, the plurality of gaseous streams including at least a vent stream and an oxygen stream.
 8. The method of claim 7, wherein the vent stream and the oxygen stream are introduced separately.
 9. The method of claim 7, further comprising mixing the vent stream and the oxygen stream after the introducing.
 10. The method of claim 7, wherein the plurality of gaseous streams further comprises an air stream and a fuel stream.
 11. The method of claim 10, wherein the vent, oxygen, air and the fuel streams are introduced separately.
 12. The method of claim 7, further comprising introducing the oxygen stream into the vent stream proximate the ceramic matrix.
 13. The method of claim 11, further comprising mixing the air stream and the oxygen stream for providing an air-oxygen mixture upstream of the vent and fuel streams, and introducing the air-oxygen mixture into the vent and fuel streams.
 14. The method of claim 11, further comprising mixing the separately provided vent, oxygen, air and fuel streams for providing a mixed stream, and introducing the mixed stream into the heated ceramic matrix. 